Ma Mai-Juan, Yang Yang, Wang Hai-Bin, Zhu Yi-Fan, Fang Li-Qun, An Xiao-Ping, Wan Kang-Lin, Whalen Christopher C, Yang Xiao-Xian, Lauzardo Michael, Zhang Zhi-Yi, Cao Jin-Feng, Tong Yi-Gang, Dai Er-Hei, Cao Wu-Chun
State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 100071 Beijing, PR China.
Department of Biostatistics and Emerging Pathogens Institute, University of Florida, Gainesville 32611, FL, USA.
Infect Genet Evol. 2015 Jun;32:148-55. doi: 10.1016/j.meegid.2015.03.001. Epub 2015 Mar 7.
Tuberculosis (TB) outbreak occurred in a boarding middle school of China. We explored its probable sources and quantified the transmissibility and pathogenicity of TB. Clinical evaluation, tuberculin skin testing and chest radiography were conducted to identify TB cases. Mycobacterium tuberculosis isolates underwent genotyping analysis to identify the outbreak source. A chain-binomial transmission model was used to evaluate transmissibility and pathogenicity of TB. A total of 46 active cases were ascertained among 258 students and 15 teachers/staff, an attack rate of 16.8%. Genetic analyses revealed two groups of M. tuberculosis cocirculating during the outbreak and possible importation from local communities. Secondary attack rates among students were 4.1% (2.9%, 5.3%) within grade and 7.9% (4.9%, 11%) within class. An active TB case was estimated to infect 8.4 (7.2, 9.6) susceptible people on average. The smear-positive cases were 28 (8, 101) times as infective as smear-negative cases. Previous BCG vaccination could reduce the probability of developing symptoms after infection by 70% (1.4%, 91%). The integration of clinical evaluation, genetic sequencing, and statistical modeling greatly enhanced our understanding of TB transmission dynamics. Timely diagnosis of smear-positive cases, especially in the early phase of the outbreak, is the key to preventing further spread among close contacts.
中国一所寄宿制中学发生了结核病（TB）疫情。我们探究了其可能的源头，并对结核病的传播性和致病性进行了量化。通过临床评估、结核菌素皮肤试验和胸部X光检查来确定结核病病例。对结核分枝杆菌分离株进行基因分型分析以确定疫情源头。采用链式二项式传播模型评估结核病的传播性和致病性。在258名学生和15名教师/工作人员中，共确诊46例活动性病例，感染率为16.8%。基因分析显示，疫情期间有两组结核分枝杆菌共同传播，且可能源自当地社区。学生中的二级感染率在同年级内为4.1%（2.9%，5.3%），在同班内为7.9%（4.9%，11%）。估计一例活动性结核病病例平均可感染8.4（7.2，9.6）名易感人群。涂片阳性病例的传染性是涂片阴性病例的28（8，101）倍。既往接种卡介苗可使感染后出现症状的概率降低70%（1.4%，91%）。临床评估、基因测序和统计建模的结合极大地增强了我们对结核病传播动态的理解。及时诊断涂片阳性病例，尤其是在疫情早期，是防止密切接触者中进一步传播的关键。
